The problem solved here is that an asp.net <button> element (html = <button runat=”server” > or <asp:HtmlButton ) doesn’t support a onclientclick event. This prevents performing client side validation ahead of the onserverclick event.

Quick Answer

Intro

I had this desperately annoying problem where I had two Combobox components. Using the .CascadeTo functionality, I was able to have the second Combobox load data via an AJAX call based on the selection in the first Combobox. This is standard functionality detailed in the demo site here.

The problem was that if the AJAX call to load the second comboxbox with data returned no elements, the Combobox remained disabled. This was unintuitive for the user and made it look like the UI had frozen.

The solution:

Add an ‘OnDataBound’ event handler to the Combobox then from this…

…. count the number of elements in the Combobox and do something to notify the user if there are no elements